The major objective of this research program is to continue investigations aimed at advancing our understanding of mechanisms by which sensory input modifies the developing primate visual system. Toward this aim we will continue studies of the effects of monocular and binocular pattern deprivation on the visual system of galagos and tree shrews. Anatomical and behavioral investigations are planned that will measure the relative permanence and reversibility of the effects of monocular deprivation. Neurophysiological and anatomical investigations are proposed that will consider the relative effects of monocular deprivation on the development of different functional subclasses of cells. Finally, experiments are planned that will investigate the effects of binocular deprivation. The following approaches will be used: (1) The effects of deprivation upon retinal and geniculate projections will be studied in galago and tree shrew with transported tracers. Also, the influence of deprivation on the growth of geniculate neurons will be investigated. (2) Response of single neurons will be studied in the geniculate of normal and deprived galagos. (3) The behavioral consequences of deprivation will be assessed in galago and tree shrew with measures of visual perimetry and visual resolution.